After you first publish an article, you can come back to it to add new information, correct a mistake, or any other reason. When you are ready to publish the updated version, you're prompted with the option to provide a reason.
As a matter of transparency, every published version of your article will be available for viewers. However, you can go one step further and provide context on why you updated your article.
If you choose to provide a reason, your followers will see an "article updated" event in their activity feed, with the provided reason clearly displayed. If, on the other hand, you don't provide a reason, the revision will still be saved in the public article history, but no event will be broadcast to your followers' feeds.
Previously, an article update event was always broadcast when updating a published article. However, the most common case for updating an article so far is realizing you made a typo, forgot something, or wanting to rephrase a sentence shortly after publishing. This would create more noise than needed in activity feeds.
Now, article update feed events are more useful & purposeful, without sacrificing the notion of keeping a complete publication history for articles.